Method of silicidizing articles containing carbon.



F. J. TONE.

METHOD 0F SILICIDIZING ARTICLES GONTAINING CARBON.

APPLICATION FILED NOV. 22, 1912.

`Patemtea Feb.25,1913.

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WITNESSES UNITED STATES PATENT OFFIGE. FRANII J. TONE, OE'NIAGARA FALLS,NEW YORII,V AssIcNoR ro THE cAREORUNDUM COMPANY, or NIAGARA EALLsNEWYORK, A CORPORATION or PENNSYLVANIA.

METHOD OF- SILICIDIZING- ARTICLES CONTAINING CARBON.

Specication of Letters Patent. Patented Feb. 25, 1913.l

Original application iled March 26, 1912, Serial No. 686,386. Dividedand this application led November 22, 1912. Serial No. 732,879.

To all whom it may concern:

Be it known, that I, FRANK J. TONE, a citizen of the United States,Vresiding at Niagara Falls,-Niagara county, New York, have invented anew .and useful'MethOd of Silicidizing Articles Containing Carbon, ofwhich the following is a full, clear, and exact y description, referencebeing had to the accompanying drawings, forming part of thisspecification, l in which- Figure 1 is a vertical cross section show inga preferred form of furnaceconstructed in accordance with my invention;and F1g..2 is. a horizontalv sectlonal view of the same.

dizing .articles containing carbon or siliconcarbid in a carbon-resistorfurnace, and is especially adapted for the conversionof shaped articlesinto silicon carbid, .such for l, examplehas the articles Obtained inthe process described in United States Letters Patent No. 992,698,issued to me on May 16th, 1911. The present application is a division ofmy pending application Serial No. 686,386, filed March 26th, 1912.

By the silicidizing of articles containing carbon or silicon carbid,-I-mean to include .I the making of all shaped articles of silicon 3o ofthe energy being available for the desired work of silicidizing thearticles to be treated. In other words, such furnaces have had a verysmall capacity in proportionto the powerused. Furthermore, uniformradiation from the resistance core into the article being treated wasnot Obtained and the articles were subjected tol displacement and otherdiiicultie My invention relates to a method of silici.

.--My inventionl is designed to provide a novel method which will betterequalize the temperature throughout the conversion or silicidizing zone,and in which more of the lpower will be consumed in a silicidizingaction, Y giving greater uniformity, greater economy of energyconsumption, and more satisfactory operating conditions.

In the drawings, in which I show one form of furnace which may be usedin carrying out my invention, 2 represents they base; 8, 3 the headwalls; and 4, 4 the side walls vof the furnace, which is preferably ofboX-like for m open at the top. The carbon electrode terminals are shownat 5, 5, extending through the head walls and suitably connected to the,source of electrical energy.

The resistance cores are shown at 6, these being shaped so that thevertical dimension is much greaterthan the horizontal dimension, thusgiving a more uniform horizontal radiation of heat from the sides of thecore into the conversion zones, which are sub- K V lar carbon, thoughother suitable resistance material may be used, and they may be of blockform or other solid shapes, if desired. .By reasonl of elongating theresistor vertllcally, I am enabled to utilize a much greater proportionof the energy radiated than with a circular core. The amount of energyradiated uselessly upwardly and downwardly .is greatly lessened onaccount Of the small amount Of surface, as compared with that at thesides of the resistor.

The silicidizing zones are shown at 7, these beingcharged, for..example, with molded articles to be converted, placed upon suitablesupports 7a.

erably substantially parallelwith and equidistant from the cores. Thethickness of the conversion zoneA is so proportioned that a goodconversion will be Obtained through- Out the zone, this being determinedby trial provided with separators of carbon or other These articles areplaced in a vertical pile, the sides of which are prefmaterial, topermit a better permeation of the silicon vapors, and care should beexercised in separating them lengthwise of the core, in order to reduceas far as possible the formation of leakage paths for the current. It isalso desirable to form the corresponding breaks in the support, in orderto prevent leakage through the base of the furnace.

S represents the embedding mixture .which preferably consists of thirtyparts pulverized coke, sixty parts silica sand and seven parts sawdust.rlhis preferably entirely surrounds the core and the articles to betreated, except that the lat-ter may be supported from the base of thefurnace. By this arrangement, the articlesl Will better preserve theirshape and keep a constant positio-n during treatment, as there is apt tobe settling and displacement of the cores.

The proportioning of the cores and the furnace dimensions willpreferably follow the practice in the Well-known granular-coresilicon-carbid furnace, the principles of twhich are Well known.

In using the furnace, it is operated in the same manner as asilicon-carbid furnace, and the run is preferably continued until themixture between the cores and the silicidizing zone is converted intosilicon carbid.

The silicidizing effect may be varied With-- in considerable limits.When treating carbon articles and carrying the temperature of thesilicidizing zone only up to the point of formation of amorphous siliconcarbid, if the time of treatment is properly extended, the carbonarticles Will be converted into amorphous silicon carbid. When a denserform of silicon carbid is desired, the operatiton is carriedv to thepoint Where the entire space between the cores is brought above thetemperature necessary for the formation of crystalline Aftertheoperation has continued for a sutiicient time to give the desired degreeof conversion, the furnace is shut down, a1- lowed to cool and thenunloaded. rllhe upper and low-er tiers of materials may be retreated, ifthey do not show the desired degree of conversion.

It is important that thesurrounding mixture shown at 8 should besufficiently porous to permit free circulation of silicon-containingvapors, and in place of using saw-f -dust or similar material for suchpurpose,

it is possible to use the silica and carbon in coarser lumps or` amixture thereof in briquet form. l have also found in certain cases thatthe addition of silicon carbid to the silica carbon mixture Will giveimproved results.. shrinkage and settlement ofA the mixture, aids in theconduction of heat from the cores to the silicidizing zones, and hascer- ,tain other advantages.

silicon carbid.

In such cases, this reduces the' The advantages of my invention resultprimarily from the increased efficiency and economy, owing to reducingthe amount of useless radiation and increasing the proportion of energyutilized by the elongated substantially parallel arrangement of thecores .and silicidizing zones. rllhe resulting articles are also moreuniformly converted and of better qualit-y.

Changes may be made in the form and arrangement of the furnace and coresand the articles to be treated, Without departing from my invention.

'l claim l. The process of silicidizingarticles containing carbon in acarbon-resistor furnace, Which consists in assembling said articles inself-supported piles broken' in the direction of 'current flow,disposing said piles along the resistor in a position to be heated bythe same, surrounding said resistor and articles With a porous mixture'capable of generating silicon-containing vapors, and passing suii'icientcurrent through said resistor to silicidize said articles.

2. The process of silicidizingarticles containing carbon in acarbon-resistor furnace, ,which consists in assembling said articles inself-supported piles broken in the direction of current flow, disposingsaid piles along a plurality of -resistors in a position t0 be heated bythe same, surrounding said resistors and articles With a porous mixturecapable of generating silicon-containing vapors, and passing sufiicient4current through said resistors to silicidize said articles.

The process -of silicidizing articles containing ca-rbon in acarbon-resistor furnace, Which consists in assembling saidarticles inself-supported piles broken in the direction of current iow, disposingsaid piles along the resistor in a position to be heated by the same,said'resistor being shaped to give a maximum horizontal radiation and aminimum vertical radiation, surrounding said resistor and articles witha porous mixture capable of generating silicon-containing vapors, andpassing sutiicient current through said resistor to silicidize saidarticles. g

4. The process of converting shaped arvfticles into silicon carbid in acarbon-resistor furnace, .Which consists inassembli'ng said articles inself-supported piles broken in the direction of current flow, disposingsaid piles along the resistor in a position to be heated by the same,surrounding said lresisto-r and articles with a porous mixture pors, andpassing sufficient current through said resistor to silicidize saidarticles.

5.' The process of silicidizin'g articles containing carbon in acarbon-resistor furnace, Which consists in` assembling said articles inself-supportedy piles broken in the direction capable of generatingsilicon-containing vacies with a, porous mixture containing silica andcarbon, and passing suicient current of current4 flow, disposing saidpiles along In testimony whereof, I have hereuntoset the resistor in aposition to be heat/ ed by the my hand. same, surrounding said resistorand arti- FRANK J. TONE.

Witnesses:

A. D. KEPOR, GEORGE W. CHORMANN.

through said resistor to silicidize said articles. v

